After reading a fascinating article about Acer pentaphyllum by William A. McNamara in Curtis’s Botanical Magazine 2011 vol. 28 (2): pp. 128–140, I decided to try and grow this endangered maple in our yard in coastal Connecticut (zone 7a). A couple of things struck me while reading the piece. First, the serendipity of the discovery of one of the known populations: “This population was first noticed by Yin Kaipu in 1987 when he was passing through the area and saw a man carrying a basket with a baby pig in it surrounded by leaves of Acer pentaphyllum.” And second, the description of the habitat: “The trees were growing on a very steep southeast facing slope with ashes, oaks, clematis, bracken ferns, mulberries, roses, hemlocks, and other species of maple above the Jiulong Jiang. None were seen on the other side of the river.” I thought that I could find a spot on our property that resembles these conditions. I chose a spot next to a large granite boulder and cleared all grass and other vegetation. The rock face next to the planting site has SE exposure and the soil is very acidic and very well draining. There is a small stream abouti 7 meters from the chosen spot and the soil in the area is shaded by the rock during the afternoon (last picture), whereas the above ground is exposed to full midday and afternoon sun. In the morning the site is in dappled shade. The large tree stump close by is from a white ash.
The tree I purchased arrived at the beginning of June from a company in the Los Angeles area. It had been cut (all branches) at about 3 ft, leaving less than 10 leaves on the plant, in order for it to fit in the shipping box. Otherwise, the tree was in a very good shape. I planted it immediately and about 10 days later there were many new shoots emerging from all branches. It is not a grafted plant, almost certainly it’s seed-grown.
The climate for the natural environment of A. pentaphyllum will be close to impossible to match in our yard. These data are for the area where the species is found (from Wikipedia):
And below are the numbers for our area. There are two major differences. The natural habitat has milder summers and (more importantly) winters. A friend of mine from Sichuan tells me that she grows exotic plants from her native region in her Connecticut garden without much problem, except that seedlings and small plants cannot survive our winters without protection. Older plants are perfectly fine. According to her, in Sichuan the temperature in winter is almost never goes down to freezing or below. (Interestingly, she had never heard of A. pentaphyllum.) The second major problem will be the precipitation. In its normal habitat, pentaphyllum experiences very wet summers and very dry winters. Here, precipitation is more or less the same year round. I am currently watering every morning, to match the weather in Sichuan, where it seems to rain almost every day in June. However, it will not be possible to match the conditions in winter. Our wet winters will likely be a problem. Time will tell.
I also decided to try and graft a small branch to a sapling of A. saccharum growing on the outskirts of our yard. I read that this was the species it was originally grafted on in the early days, quite successfully long term. My grafting skills are almost nonexistent, but fingers crossed… That could be a way to get over the “wet feet in winter” problem, having local saccharum roots. If unsuccessful, I will keep trying.
In the fall of last year, a new population of A. pentaphyllum was discovered in Sichuan: https://cbcgdf.wordpress.com/2024/0...establish-a-community-conservation-areaccafa/
20 days after planting, the new growth is doing well. Pictures from late afternoon today after strong storms delivered good amount of rain (no need to water it tomorrow morning!).
One observation that may be useful to others growing pentaphyllum: I noticed that it simply detests low humidity when it is actively growing. Especially if it is combined with strong winds. Some leaflets or entire young leaves will just wilt and then die. I hope I can prevent this in the future by giving it extra water during the growing season on days with low humidity. I already use about 10 L/day, but the planting site is such that it dries out very quickly. Planning to triple the volume of water on dry/windy days.
How cold it gets in mountainous Sichuan will depend entirely on what altitude an involved growing site is located at.
I hear you on the deer issues. Same problem here. I've only ever seen it on pseudoplatanus, not very successfully. The seedlings do better, but it is unpredictable. They don't seem to like very cold (-10C). I had planted a small grove, decent sized at around 1.75m, all doing well. Then they all died the same winter. Cold? Wet? Hard to say. Even the seedlings in pots are unpredictable, they seem to just croak for no apparent reason, or die way back. I have a new batch of seed stratifying now. -E
Wet. Based on the climate in their native habitat, I strongly believe that the problem is too much moisture in winter.
Maybe. The grafted one lived for a long time (but died back in winter) in a pretty wet spot. They all died the same winter, including the graft, that wasn't particularly wet; and the seedlings were planted in a very well drained place. The seedlings that die randomly are kept completely out of the wet all winter long.
See related narrative at bottom of page linked to below. Including This beautiful, unusual species has been in cultivation in the West for only about 85 years, originally introduced from no more than three individual plants. There are few if any seedlings derived from this early introduction, and grafted plants from the original stock are notoriously frost tender and feeble in northern gardens Maples - UBC Botanical Garden
@Ron B , there is no doubt you are full of knowledge, but it would be nice if you could just say what you mean, instead of being ambiguous. If you really are a horticultural scientist, as you imply to be (and I am sure you are), you should have no problem saying succinctly and precisely what you have to say. Language is just as important as data. Some times you are very clear, not in this case.
This part of the article is in error. Acer pentaphyllum found the climate in parts of Australia very favourable and specimens there have been producing large amounts of good quality fertile seeds for many years, certainly pre-dating seed collecting expeditions to China in the early 2000's. There are many mature seed grown specimens in Australia and also seeds from these trees have been distributed internationally among amateur growers. I guess that was what Emery was referring to. The seed collecting expeditions to China to increase the genetic diversity of plants in cultivation in the west are obviously a good thing, but by no means the only source of seedlings.
In addition to a comment by @maf in a different thread that one cannot overdo the amount of sunlight it gets, I would like to suggest that the amount of water it receives when it’s growing (summer) cannot be overdone either. Ever since I started giving it more than 30 L of water every morning (even after rain), not a single leaf has dried out, even though it has been very hot and very sunny lately. It seems to love it.
It’s almost the end of August and pentaphyllum continues to grow. I have slightly reduced the amount of water it gets every day. Planning to continue watering until the end of September and rely entirely on rain after that.
For what it's worth, adopting to various typical 'maritime climates' hasn't proven a problem, at all, for the vast majority of Chinese plants. Or adopting to year-round rainfall (if erratic!) climates like the eastern US. Having 'too much' water when the plant is dormant tends not to cause the problems that the converse scenario causes. (i.e., too much water when actively growing) There are, of course, exceptions; an example would be plants that naturally grow in subtropical highland climates as epiphytes. They can rot during wet winters. Also, things that come from plant families of dubious hardiness, anyhow. To the degree I've been able to keep various Cycas panzhihuaensis alive over the decades, they've had a better time surviving in anomalously dry winters. The Scott Arboretum in SE PA supposedly has several A. pentaphyllum, pre-dating the polar vortex winters. Next time I'm there I'll try to find them and take some pictures. Between that garden and Chanticleer you will generally find the most compelling experiment outdoor plantings in the Philly suburbs. Longwood is afraid to plant anything that might end up not looking 100% perfect.
I was so excited to read this. Unfortunately, when I checked their plant explorer app, pentaphyllum is listed as no longer alive. The Morris and Arnold arboreta don’t have it, and neither does the New York BG. I am not aware of any public access garden in the Northeast that has it its collection. Hoping this is not a bad sign for my efforts, plus our yard has its own microclimate… time will tell.
I was wrong. Chanticleer has one and it has survived there for 12 years! Interestingly, the source was Morris.
It is encouraging that Chanticleer is also in zone 7a, although I am not sure what “deep frame” means about the location of their pentaphyllum.
Well thanks for confirming my source for Scott Arboretum data is out of date. It is: https://websites.rbge.org.uk/multisite/multisite3.php Although I was aware of their Explorer, the link above is more convenient for querying all US Sites. I guess you already checked the National Arboretum? I have a vague memory I might have seen one at another SE PA garden more recently...I haven't been to Chanticleer in almost 15 years! (need to get back) Give me a few weeks, I'm planning on organizing some old smartphone pics anyhow.
